Abstract

We demonstrate efficient third harmonic generation of a near infrared femtosecond pulse through cascaded frequency doubling and sum-frequency generation processes, where the group velocity mismatching between the involved fundamental and generated second harmonic pulses, before they are sent to frequency mixing, are precompensated with a properly inserted nonlinear crystal. The spectrum of the generated third harmonic pulse with energy of 1.1 mJ is further modulated by using impulsive molecular alignments of , , and , where significantly broadened spectrum in the ultraviolet spectral region is observed due to the additional cross-focusing effect from the parallel aligned molecules and the consequently enhanced self-phase modulation.

Received 03 August 2009Accepted 21 December 2009Published online 20 January 2010

Acknowledgments:

This project was funded by the National Basic Research Program of China (Grant No. 2006CB06001), the Program for Chingjiang and Innovative Research Team in University; Shanghai Academic Discipline Project (Grant No. B408).